The present invention relates to a multi-window display control for operating an existing application program for a non-window system in parallel with an application program for a window system in the window system of a personal computer and a work station.
A multi-window system and a color graphics system are disclosed in papers of Jon Udell, "Three's the One", BYTE, June 1990, pp. 122-128, Ray Duncan, "Microsoft Windows/386: Creating a Virtual Machine Environment", MICROSOFT SYSTEMS JOURNAL, September 1987, pp. 01-11, and R. F. Ferraro, "Programmer's Guide to the EGA and VGA Cards", Addison-Wesley, pp. 8-13 and 596-601.
Recently, in order to improve the user interface, many personal computers and work stations introduce a window system, as a basic software, in which a plurality of windows are displayed on a display screen by the graphics and a plurality of application programs can be operated on the windows by a pointing device such as a mouse.
The application program for the window system in which the graphics function provided by the window system is used to make display in one window is different than the existing application program for the non-window system which uses an operating driver of the operating system or directly accesses display hardware to display text or graphics on the whole display screen, therefore the application program for the non-window system is usually not operated on the window system. Thus, software properties such as current application programs and user's software for the non-window system accumulated from the advent of the personal computer and the work station cannot be utilized in the window system.
Thus, in the window system that places importance on interchangeability, in order to operate an existing application program on the window system in the same manner as the application program for the window system, the multi-window display in the window system is made by physical display hardware. Meanwhile access to the display hardware from the application program for the non-window system in which display is made on the whole display screen adopts a method in which a virtual VRAM established in a main memory is used to emulate the physical display hardware. Accordingly the application program for the non-window system is operated in the window system and contents in the virtual VRAM are further periodically transferred and displayed by the graphics function of the window system so that operation is made as if the application program for the non-window system is displayed in the window.
The emulation of the display hardware requires an emulation process of hardware for writing in the VRAM data from a CPU which emulates access to the display hardware from the CPU and an emulation process for emulating hardware for displaying data established in the VRAM. Further, the display hardware includes text display hardware for displaying text, and graphics display hardware for displaying graphics.
In the text display, since access to the VRAM is made in the same manner as the usual access to the main memory, it is not necessary to emulate the access to the VRAM with respect to the virtual VRAM, and therefore emulation of the CPU can be easily made. Further, character codes and attributes written in the VRAM are periodically taken out by an application program or a display driver and a text is developed or expanded in the window by means of the graphics function of the window system, so that emulation of the display hardware can be made relatively easily.
On the other hand, it is relatively easy in the same manner as in the text display to develop graphics data developed in the VRAM by means of the graphics function of the window system and emulate the display hardware. Meanwhile emulation of the CPU hardware requires complicated control and practical display performance cannot be ensured since the CPU hardware adopts a VRAM having a plane structure in which a plurality of sets of memories are assigned to the same address in accordance with the number of colors, and the CPU can access the memories corresponding to the colors simultaneously in order to make drawing such as painting-out at high speed.
Accordingly, heretofore, display in the window of the application program for the non-window system is often limited to an application program using only the text display hardware.
Still another problem is that when the application program for the non-window system displays data in the window of the window system, space for a window frame is required, and accordingly a display size is made smaller than the whole display screen even if a user area of its window is expanded to the maximum size. In this case, since the whole display screen of the application program for the non-window system in which the whole display screen is used for display cannot be displayed in the window at one time, it is necessary to operate the application program while frequently scrolling the display and there is a problem that operativity is deteriorated.